310 ALDA GRACE BARBER 



Rat No. 4 raised his averages, January 29 and 30, by making 

 three bad reactions each day. The other trials however, were 

 of normal accuracy. Rats No. 20, 21, 22, 23, were tested after 

 a rest period of nearly a month (Feb. 11-Mar. 8) Table VIII. 



The younger rats, No. 20, 21, 22, 23, seemed less certain of 

 the correct response than did the older rats, particularly No. 6, 

 but retention was evidently present. No. 22 broke down on 

 the first two trials given, making an average of only 5-6 on 

 the last six. No. 21 seemed indifferent to the stimulus as a 

 rule, although he made several perfect reactions. The small 

 number of rats used however will not permit correlation between 

 age and accuracy of memory. It must be remembered that 

 although the rats were not tested during the period of rest, 

 they still had some practice in that they would run to the sides 

 of the cage when anyone entered the room. This however will 

 not account for the accuracy manifested in the memory test. 



SUMMARY AND CONCLUSIONS 



1. The white rat is able to localize a noise with an average 

 accuracy of from 2 to 4 inches under the conditions of the pre- 

 sent experiment. This means, of course, 2-4 inches on either 

 side of the point of stimulation, so that while in a single trial 

 the accuracy is as just stated, and, let us say, to the right of 

 the source, the next time it may be an equal distance to the left. 

 The total space covered is, therefore, from 4 to 8 inches. 



2. The association between such an accuracy of localization 

 and food is established in from 40 to 136 trials. 



3. The response is to an auditory cue, for those from vision, 

 odor and kinaesthetic-tactual sources were eliminated from the 

 experiment without change in the accuracy of response. 



4. The auditory factor which in general determines the accur- 

 acy of localization is probably the relative intensity of the 



